An air turbine starter (ATS) is typically used to start an aircraft turbine engine, for example, a gas turbine jet engine. The ATS is typically mounted to the jet engine through a gearbox or other transmission assembly and a cover plate or wall is located between the starter and gearbox housings. The gearbox transfers power from the ATS to the engine to start the engine.
Many air turbine starters typically include lubrication to run properly. Some air turbine starters use an assisted wet cavity design (AWC) to assist in lubrication. These designs include a turbine starter housing having a mounting face or mounting flange that is sealingly engaged with, and coupled to, the gearbox such that a porting system, that allows transfer of lubricating oil between the gearbox and the starter, is defined. Each port in the porting system is typically in fluid communication with passages within the starter housing so that oil can be distributed within the starter, and are located in portions of the starter-gearbox assembly such that they act as sump passages or oil return passages. The transfer of lubricating oil is intended to keep the oil within the starter housing fresh and clean.
Typically in AWC designs, fluids flow from the gearbox into an enclosure that is attached to the housing of the starter. This enclosure is in fluid communication with the starter. The exchange of oil between this enclosure and the starter is governed by movement of the fluid during aircraft operation, mechanical stirring within the starter, fluid diffusion and incidental fluid agitation caused by the fluid stream from the gearbox. The resulting exchange of fluid does not keep the oil as fresh as desired. The gearbox may be pressurized at about 0.1–6.0 psi above ambient pressure. Though highly unlikely, it is postulated that the starter housing may become punctured, causing a breach in the starter structure and a change in pressure. In such a highly unlikely instance, the starter pressure may drop to equalize with ambient pressure. Consequently, the pressure differential between the gearbox and starter may be about 0.1 to 6.0 psi. If oil is continuously fed to the starter during starter housing breach, excessive oil may still leak from the gearbox to the starter and, consequently, out through the breach even though the pressure differential is relatively small. Eventually, sufficient oil is lost that may cause problems in the gearbox. U.S. patent application Ser. No. 10/732,935 describes check valves that may be used to counteract the oil loss. However, because the pressure differential between the starter and gearbox can be small, these valve types may not work consistently.
Accordingly, there is a need for an aircraft turbine starter that allows fresh oil to freely flow from the gearbox to the starter, but can safely discontinue flow in the condition of starter housing puncture. Additionally, there is a need for an air turbine starter with the ability to operate during starter housing breach, and in particular, in instances when the breach causes a low pressure differential between the starter and gearbox. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.